Bought this 1988 Silverado bout a year ago.There has always been a sound similar to a fan running under the dash on the passenger side, when I shut the engine off....Stops after 10 seconds or so........The seller said it has always done that....Should I be concerned???

 

I had an 89 that done that. It is just the A/C fan finishing turning after you turn the power off. I eventually changed it out. It sits inside that shroud that covers it.
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